1. Field of the Invention
The present invention relates to a novel process for producing tofu (bean curd).
2. Description of the Related Art
Tofu is roughly divided into two types, momen (pressed) tofu and silken tofu. In a traditional manner, both momen tofu and silken tofu are prepared by pouring hot soybean milk just squeezed out into a mold, mixing natural coagulants such as MgCl.sub.2 and CaCl.sub.2 into the soybean milk and stirring, and allowing the mixture to stand to completely coagulate. In preparing momen tofu, the coagulated product in the mold is transferred into a wooden draining frame with cloth lying therein, then pressed to drain part of contained water and shaped. The resulting tofu is then cut to size and immersed in water. In preparing silken tofu, coagulation is completed within the mold, and the resulting tofu is cut to size and immersed in water.
A traditional manner for preparing tofu ensures stable coagulation by conducting coagulating operation on ten to tens pieces scale.
In recent years, the production of tofu is on the trend of large scale and mechanization. Even in this case, however, tofu is actually produced in a method which follows the traditional production method as closely as possible.
On the other hand, there have been proposed a method for dehydrating and forming coagulated soybean milk in a production device of tofu which has been practiced in both momen and silken tofu preparations (see Japanese Laid-open Patent No. 2-295453 and No. 2-312564). This method draws attention from the standpoint of practicability for mass production, convenience in distribution, hygiene, and so forth. The preparation adopted in this system is to fill a mold with cold soybean milk containing a coagulant and then to heat it.
In the meantime, the structure of tofu consists of net structure between soybean proteins formed by coagulation. The study of the inventors have revealed that the taste of tofu depends on whether the net structure is uniform or non-uniform. While the structure of tofu varies according to the raw soybeans, the method for preparing soybean milk, the protein concentration of soybean milk, the kind and amount of the coagulant and the like, in tofu prepared in the traditional method, a coagulant is added to hot soybean milk, so that coagulating reaction starts immediately after the addition of a coagulant to thereby form non-uniform tofu structure.
On the other hand, in the mass production method taught by the prior art publications mentioned above, the soybean milk is cooled enough to suppress coagulating reaction from mixing natural coagulants to filling it into a mold as much as possible, and then the soybean milk thus filled in the mold is heated so that coagulating reaction proceeds. Accordingly, the structure of the resultant tofu is uniform, and the texture of silken and that of momen tofu formed from collapsed silken tofu as well do not match the texture of traditional tofu. That is, the collapsing-in-the-mouth texture of tofu as given by traditional tofu makes tofu really tasty, but unfortunately the machine production fails to produce such tasty tofu.
While the texture is influenced by such conditions as the method for preparing soybean milk, the protein concentration, the kind of the coagulant, and the like as mentioned above, it is extremely difficult to vary the texture quality of tofu simply by somewhat altering these conditions.